A heat exchanger has a collecting pipe, a separator and a number of heat exchange tubes. The collecting pipe has a pipe wall and an inner cavity. The separator is provided in the inner cavity. The separator extends along a lengthwise direction of the collecting pipe. The separator divides the collecting pipe into a first cavity and a second cavity. The heat exchange tubes are arranged along the lengthwise direction. Each heat exchange tube has a first end and an inner cavity. The first end of the heat exchange tube sequentially passes through the pipe wall of the collecting pipe, the first cavity and the separator to be inserted into the second cavity. The inner cavity of the heat exchange tube is communicated with the second cavity. As a result, uniformity of refrigerant distribution in the heat exchanger is improved.